Abstract: Basing upon the recent field investigations, the principal features of the NW trending fault structure in Yanshan region are summarized in this paper.By analyzing structural, seismological and geophysical data, the authors demonstrated the space distribution, formation, development and movement mode of the NWW trending basement fault zones, as well as their relation to the seismicity. It is suggested that the NWW trending fault zone can be attributed to a crustal fault, controlling both the development of fault block structure and the recent seismicity. The fact that the NW faults spread en echelon and cluster into a zone is a indication of a NWW fault zone in the superficial strata. Moreover, the movement mode of the zone under investigation has a very close relation with the relative motion of the fault block structures. Since Mesozoic and Cenozoic periods, in addition to the differential movement, this fault zone was of shearing motion which had a very obvious changes in nature during the periods from Late Cretaceous to Early Tertiary.